transmission question

[283nova]

is it odd that a 60 gmc 1/2 ton fleet would have a 4 speed hydromatic tranmission behind the 305 v6? or is that just what they came with for an automatic?

[padresag]

that is what they came with from about 53 or 54-62. Same hydramatic as used in 54-56 olds and caddies.
why is it odd?
ron

[kalirodding]

What 4 speed?

[padresag]

Originally Posted by kalirodding

What 4 speed?

what are you questioning
ron

[283nova]

was unsure, thought they had 3 speed hydromatics

[markeb01]

It isn’t “odd”, but it certainly is rare. Automatic transmissions in any of these trucks were rare, even more so with the GMC’s.

The 4 speed Hydramatic was also the basis for the famous B&M Hydro Stick racing transmission. They were industrial strength (and very heavy) and could be made to really slam into gear, and the first automatic transmission to be competitive against a stick shift. Here are a couple of comments from the B&M website:

“In the 50s it was B&M who came up with the idea of using a performance reinforced Hydramatic for racing”.

“B&M Automotive Products was founded by Bob Spar and Mort Schuman (B&M) in 1953. In 1955, Bob's brother Don went to work for B&M. Soon after, B&M produced the only patented 4-speed automatic racing transmission in history, known as the famous B&M Hydro Stick”.

[padresag]

they were not that rare. I just got rid of one a few months ago that I had.
ron

[paul63c10]

I have a jasper 350 sbc and a 2 speed powerglide behind that. what effects will that have on the 350 and original rear end? not to mention my daily driving habits?

[fleetsidelarry]

Originally Posted by markeb01

“In the 50s it was B&M who came up with the idea of using a performance reinforced Hydramatic for racing”.

Markeb, there was an informative writeup in the Shopmanual section of the January, 2010 issue of Street Rodder magazine about these transmissions, in which, along with other information, similar statements were made. A reader responded (in the March issue) with the clarifying information that, in fact, a Cadillac Motors employee (Jack Leidgen, who had been involved with the development of the heavy-duty hydramatic tank transmission parts), was building racing hydramatics as early as 1950 and that, in 1951 (2 years before B&M), Cadillac published a spec sheet listing the parts that would be used to build a modified hydramatic and that these were the parts used (at least early on, I assume) by B&M.